This research intends to increase the sensitivity and prognosis value of molecular imaging with 18FDG- PET/CT of small (<1 cm in diameter) malignant lung lesions that move significantly during respiration. The long-term objective is to provide an early and more accurate diagnosis and prognosis of malignant lung lesions than is currently available. The importance of this research is to develop and validate a practical and low cost solution to the problem of respiratory motion for the accurate interpretation and quantitation of 18FDG uptake of lung 18FDG-PET images. Currently there is no validated practical methodology that can be applied to compensate for respiratory motion in lung PET studies. The solution to this problem would improve the identification and accuracy of 18FDG uptake quantitation of small lesions. Improving the detection of a malignant lung lesion in its initial stage will positively impact the care of patients with lung cancer, a major health problem in the United States. This research will be conducted by: a) developing and validating a respiratory-gating system based on the reflection of structured light as a function of the respiratory motion, b) verifying the accuracy of the respiratory-gating system by developing and using a physical phantom that simulates the motion of the abdomen and lung lesions during the respiratory cycle, c) developing and validating a motion track computer-assisted algorithm for the integration of lung PET images at different gated time bins into a reference time bin within the respiratory cycle, and d) verifying the accuracy of the motion track algorithm for detection of lesions and 18FDG uptake quantitation by conducting experiments with the physical phantom and computer simulations using the four-dimensional (4D) NCAT computerized phantom. By integraging the counts of gated time bins into only one referenbce bin, the best compromise between noise and PET scan time can be achieved, and clinical analysis would be easier and faster. All the development and research work of this project is oriented to demonstrate the feasibility of the practical implementation of inexpensive software and hardware tools for compensating respiratory motion into the clinical setting. Results of this project will provide research tools and preliminary data for initiating clinical research oriented to the detection and identification of small (<1 cm) malignant lung lesions using 18FDG-PET. Results of this research will also be useful in planning radiation therapy of lesions that move significantly during respiration. [unreadable] [unreadable]